Hi guys, I'm taking apart an NEC monitor for it's flyback xfrmr. I've stripped it down to its bare bones, all casing/circuit boards removed. Can I disconnect the windings from the picture tube or is it a sealed assembly?
What I remember for old TVs is that the yoke is clamped to the neck of the CRT. Loosen the clamp and you can slide out the yoke. I am not sure about the NEC monitor. if no clamp, probably glued or something.
Quote from: Farlander on September 21, 2008, 06:48:31 PM
Hi guys, I'm taking apart an NEC monitor for it's flyback xfrmr. I've stripped it down to its bare bones, all casing/circuit boards removed. Can I disconnect the windings from the picture tube or is it a sealed assembly?
the cable is clamped (under the rubbershulding) witt an double clamp.
move cabel (with the rubbershilding : left and right , this way can be discinnect
GP
Thanks I loosened the two strap clamps (didn't even see them at first) at removed the plastic rings (arduously) and slid the transformer off over the neck of the CRT.
Does anyone know how to find the negative lead? And do I need to have all of the circuits connected or will the xfrmr work without any picture input? I was thinking I'd leave off the pins that seem to control video input, and just apply main power, I believe it will still pulse at the same refresh rate? Any direction would be appreciated.
You may want to consider to evacuate the tube first. Remove the socket Guide on the end of the CRT Break off the little glass tit under the socket and let the air rush in. Play it safe a tube accidentally broken can and will send slivers of glass everywhere when it implodes.
It also removes most of its stored charge.
I would forget about using the existing circuit since you removed the Yoke which is likely part of the Circuit.
You are better off to remove the Flyback and start fresh by winding a few turns of #16 wire around the core number of turns is depending on your input voltage and a bit as far as the Ratio is concerned.
There are many sites that post schematics for Flybacks using 555's or discrete flip flop's
Just google for them its far less complicated and messy and it works great.
I used a 555 and a TIP41C with 12Vdc or you could use the original HOPT as they usually have a higher voltage rating(but make sure you Heatsink it ) . If your flyback has no tripler build in like TV's in the 70's did then you can get a tripler
depending of course what voltage you want.Most recent sets have the tripler build into the Potted Casing as well as the focus rect. and pot
Worked for Sylvania long ago, had to change hundreds of CRT's, hated it, but I am still alive although we had accidents.Play it safe.
professor
Quote from: Farlander on September 21, 2008, 09:58:08 PM
Thanks I loosened the two strap clamps (didn't even see them at first) at removed the plastic rings (arduously) and slid the transformer off over the neck of the CRT.
Does anyone know how to find the negative lead? And do I need to have all of the circuits connected or will the xfrmr work without any picture input? I was thinking I'd leave off the pins that seem to control video input, and just apply main power, I believe it will still pulse at the same refresh rate? Any direction would be appreciated.
wow what a mess. I disconnected all the harnesses without marking which went where, so now I'm not sure I could use the existing circuit if I wanted to...
Thanks for the advice professor, I'm going to try and decode the wiring a little more and then hopefully attach a pwm to the primary.
What do you mean by the original HOPT? Hopefully tomorrow I'll get some pictures up for better clarification.
Sorry Farlander its short for Horizontal Output Transistor meaning the one mounted on a Heatsink on the Motherboard. Likely a 2SDxxxx
professor
Quote from: Farlander on September 21, 2008, 11:22:11 PM
wow what a mess. I disconnected all the harnesses without marking which went where, so now I'm not sure I could use the existing circuit if I wanted to...
Thanks for the advice professor, I'm going to try and decode the wiring a little more and then hopefully attach a pwm to the primary.
What do you mean by the original HOPT? Hopefully tomorrow I'll get some pictures up for better clarification.